JP3500969B2 - Electronic throttle control - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic throttle control device for an automobile, and more particularly to an automobile throttle valve control device suitable for controlling a throttle valve using a motor. 2. Description of the Related Art As a conventional throttle valve control device for a vehicle, for example, an electronic throttle control for controlling a throttle valve attached to an intake pipe by a motor in order to adjust an amount of air taken into an engine. Devices and the like are known. [0003] To control the opening of the throttle valve,
Generally, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-303285, a microcomputer or the like is used to detect the opening of a throttle valve by a potentiometer or the like directly connected to the rotation axis of the throttle valve, and the microcomputer detects the opening of the throttle valve via an A / D converter. And the arithmetic control is performed such that the detected opening becomes the target opening. Also, as described in, for example, Japanese Patent Application Laid-Open No. 6-54591, a current flowing through a motor for rotating a throttle valve is chopper-controlled by an H-brick type chopper circuit or the like composed of a power MOSFET, and a current flowing through the motor is controlled. It is also known to detect and feed back to a microcomputer and output the result of feedback control calculation as a PWM signal from the microcomputer to control. Conventionally, in the control of the throttle valve, both the opening control (position control) and the current control are performed using a microcomputer. In order to improve the performance of the electronic throttle, it is required to increase the response of the opening control, which requires a high-speed microcomputer having a high calculation speed. In particular, a high-speed microcomputer is indispensable for the current control in the minor loop of the opening control. However, high-speed, high-performance microcomputers are expensive, and when used in electronic throttles, the price of the entire control unit increases, and it is impossible to provide an inexpensive control unit. An object of the present invention is to provide a low-cost electronic throttle control device using an inexpensive microcomputer without requiring an expensive microcomputer for the electronic throttle device. Another object of the present invention is to provide a throttle valve control apparatus for a motor vehicle in which control accuracy is improved by improving response of motor current control. It is another object of the present invention to provide a throttle valve control device which can cover a response delay of a switch even when a power element having a low switching speed is used for an H-bridge chopper for controlling a motor. In order to achieve the above object, according to the present invention, there is provided a throttle valve, a motor for driving the throttle valve, and a chopper control of a current flowing through the motor to rotate the motor. -Bridge chopper for controlling the current control, analog current control means for supplying a pulse width modulated control signal (PWM) to the H-bridge chopper, and current detection means for detecting and feeding back the motor current to the analog current control means And a control means for supplying a current command signal and a forward / reverse rotation signal of the motor to the analog current control means via a filter to control the opening of the throttle valve, and detecting the opening of the throttle valve. Means for feeding back to the opening control means, and means for supplying a throttle valve opening command The opening control means generates a current command to the analog current control circuit based on the opening command and the opening feedback signal, and the analog current control means uses the current command and the motor current feedback signal, The PWM control signal supplied to the H-bridge chopper is varied, the current of the motor is controlled by the H-bridge chopper, and the motor is rotated to control the opening of the throttle valve. In the above-described throttle valve control apparatus for an automobile, the current control means uses an analog system comprising an operational amplifier and the like, and is constituted by PWM generation means, current detection means, and current deviation calculation means. It is. The above-mentioned PWM generating means is constituted by a variable frequency PWM comprising an integrator and a comparator. The current detection means includes a battery current detection resistor connected in series to the H-bridge chopper, and means for amplifying a voltage across the current detection resistor.
A / D conversion means for converting the voltage signal into a digital signal. In the current detecting means, the amplified signal is sampled and held by a sample and hold circuit which samples and holds the signal in synchronization with a fall of the analog PWM signal. The throttle opening control means receives a throttle opening command from a higher-level engine control means or the like by a communication means or the like using a microcomputer, and inputs a feedback signal of the throttle opening degree to perform a control calculation to generate a current command. Means for generating an analog signal via D / A or means for generating a current command as a duty signal by PWM are provided to control only the opening control. Further, the throttle opening control means includes:
An inexpensive low-speed microcomputer with a slow processing time is used to generate a motor current command value necessary for opening control and a forward / reverse rotation signal of the motor to control only the throttle opening. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a control system configuration diagram of an electronic throttle control device according to an embodiment of the present invention. The microcomputer 1 receives an opening command of a throttle valve attached to an intake pipe of an automobile engine from an interface 2 through a communication means from an upper engine control unit. An opening of a throttle valve rotatably attached to the throttle body is determined by an opening sensor (TPS) 3 coupled to a rotation shaft of the throttle valve.
Is detected by The opening of the throttle valve detected by the opening sensor 3 is amplified by the operational amplifier 4 as a throttle opening signal, input to the A / D input of the microcomputer 1, and output by the A / D converter built in the microcomputer 1. It is converted to a digital signal. The microcomputer 1 performs an opening control operation based on the input throttle opening command and throttle opening signal, and outputs a current command to the analog current control 5 via the filter 6. The current command from the microcomputer is output while changing the duty of the PWM, but may be output via a D / A built in the microcomputer. Further, the microcomputer 1 outputs a forward rotation signal and a reverse rotation signal of the motor 8 to the H-bridge chopper 7. In the analog current control, a current command from the microcomputer 1 and a motor current detection signal detected by the shunt resistor 9 are input as a feedback signal to perform current control.
Then, the PWM signal is supplied to the H-bridge chopper 7. In analog current control, feedback control is performed so that the current command from the microcomputer and the detected motor current are the same. For more information about analog current control,
This will be described later with reference to FIGS. The H-bridge chopper 7 is composed of four power MOSFETs for PWM control, and controls the DC motor 8 to rotate forward and backward.
Controls reverse rotation and current flowing to the motor. Also, H
The bridge chopper 7 has a gate circuit 72 for driving a power MOSFET 71, and can be directly driven by forward and reverse rotation signals from the microcomputer 1 and a PWM signal from analog current control. A watchdog timer 9 for activating the microcomputer normally and detecting an abnormality is also provided. Next, FIG. 2 shows a time chart of the analog control and the software processing of the microcomputer. The figure shows the relationship between control contents and processing timing.
Current control and PWM control that require high-speed processing are performed by analog control, current command generation and opening control are performed by medium-speed processing, and other controls are performed by low-speed processing. That is, the current control operates independently of the microcomputer, and only when a current command or the like is given from the microcomputer, it is sufficient to perform control such that the current is in accordance with the command. That is, the microcomputer only needs to perform the medium speed processing and the low speed processing, and the current control does not become a load on the microcomputer. Therefore, a low-speed microcomputer can be used as the microcomputer. The structure of the electronic throttle control device for a vehicle using the present invention will be described in more detail with reference to FIGS. First, FIG. 3 shows a control block diagram of the electronic throttle control device. The control of the electronic throttle is composed of three control systems, the current control system is analog control,
The opening control system and speed control system are controlled by microcomputer. In the current control system 5, the output value of the motor current detector 51 which detects the current flowing through the motor and the speed control system 11
, That is, the current command value, and the analog current control unit 52 performs a control operation based on the deviation, and outputs a duty signal from the analog PWM circuit 53. This current control system detects the voltage flowing across the shunt resistor 9 connected in series to the H-bridge chopper by detecting the current flowing through the motor 8 as described with reference to FIG. The actual motor current is detected from the value. As shown in FIG. 3, the current control system further includes a calculation unit 54 for comparing the current command value with the actual current value and calculating the deviation. In the current control 52, a compensation operation is performed based on the deviation obtained by the deviation operation unit 54, and an analog voltage serving as a duty command is output to the PWM circuit 53. P
The WM circuit 53 converts the analog voltage into an ON / OFF duty signal, and outputs the PWM signal to the H bridge chopper 7.
An M signal is output. In the H-bridge chopper 7, a 15
And the PW output from 53
The chopper operation is performed in response to the M signal, and the motor 8 attached to the throttle body 10 is driven. In addition to the motor, a throttle 101 for reducing the rotation of the motor, a spring 102, a throttle valve 103 for adjusting the intake air amount, a valve opening sensor 3 and the like are attached to the throttle body 10, and the valve 103 is opened and closed by the rotation of the motor. You. The current control system will be described later with reference to FIGS.
This will be described in detail with reference to FIG. Another control system is a speed control system 11 for a throttle valve. This control system has a function to add a correction value considering the opening and closing speed of the throttle valve to the throttle valve opening command value to eliminate overshoot of the throttle valve opening control and to shorten the time to reach the target opening as soon as possible. have. This control system has a throttle speed detector 12 for detecting the valve speed from the amount of change in the valve opening. The deviation between the output of the throttle speed detector 13 and the output of the opening control 13 is obtained by a deviation calculator 14. The output is calculated by the speed control unit 11 and the current command is output to the current control system 5. At the same time, a signal in the rotation direction of the motor 8 is given to the 15 opening / closing direction driving units based on the calculation result obtained by the 11 speed control units. The last one of the control systems is a throttle opening (position) control system. This control system converts a throttle opening command input from an engine control unit of an automobile (not shown) and an actual throttle valve opening obtained by amplifying an opening signal of an opening sensor 3 incorporated in the throttle body 10 by an amplifier 16. The deviation is obtained by comparison in the comparison operation unit 17. The deviation signal is input to an opening control 13 to perform a proportional and integral (PI) compensation calculation, and a feedback control is performed so that the actual opening of the throttle becomes the same as the throttle opening command. In the above-mentioned electronic throttle control, the current control system of the motor, which is required to have a fast control response, is analog-controlled, and the opening control and the speed control of the slot valve, which can be performed later than the current control, are performed by a microcomputer. The control method was used. In this case, for example, by performing the arithmetic processing of the microcomputer every 3 ms, the load factor of the microcomputer can be reduced and a low-cost low-speed microcomputer can be used. Next, FIG. 4 shows a detailed diagram of the hardware of the control system configuration shown in FIG. An opening signal is input to the microcomputer 1 from a higher-level engine control unit to a reception terminal RXD of the microcomputer via an interface composed of R11 to R13 and a buffer 21 to a TCM-RX terminal. Also, the interface buffer 22, resistors 14, 15 and power MOSFET 23 are transmitted from the TXD terminal of the microcomputer.
An accelerator opening signal is exchanged from the TCM-TX terminal to the control unit through bidirectional communication via the. On the other hand, the actual opening of the throttle valve is obtained by amplifying the signal of TPS1 from the above-mentioned opening sensor 3 by the operational amplifier 4 composed of the amplifier 41 and the resistors 17 to 19 and inputting it to the input terminal AN4 to the A / D converter in the microcomputer. Input via AN7. The opening signal of the throttle valve is of a dual system for safety, and the signal of TPS2 is also taken into the microcomputer. The TRSs 42 and 43 inserted on the TPS-VCC side on the power supply side operate as switches and are used for checking disconnection of the sensor. Also, 2
Reference numeral 3 denotes a clock generation circuit for operating the microcomputer. Reference numeral 9 denotes a power supply circuit having a watchdog function, which includes a power supply IC 91, resistors R30 to R34, capacitors C11 to C14, a transistor T1, a diode D1,
The microcomputer D1 has a power supply, a watchdog, and a reset function, and performs a program start and a reset operation of the microcomputer 1. Next, the configuration of analog current control will be described. 4 shown in FIG. 4 is an analog current control circuit. 5
Is composed of 51 deviation amplifiers and 52 variable frequency PWM circuits. Further, a deviation amplifier 51 includes an operational amplifier OP1, input resistors R50 and R51, feedback resistors R52 and R53, and compensation capacitors C51 and C51.
After the current command converted into the duty signal from the microcomputer 1 is smoothed by the filter formed by R61 and C61, the Vmc signal is input to the + terminal of the operational amplifier OP1 of the deviation amplifier of 51 by inputting the input resistance R51. Is entered via On the other hand, the feedback signal is the battery current Ib
Is detected by the current detection circuit 53 and the negative terminal of the operational amplifier OP1 of the deviation amplifier 51 is input via the input resistor R50 so that the current command value and the detected current match. An analog signal is output from the output of. Next, the variable frequency PWM circuit 52 will be described. At 52, OP2 is an operational amplifier having input resistors R54 and R55 and a feedback capacitor C53 to form an integrator. The other operational amplifier OP
Reference numeral 3 denotes a comparator having hysteresis with input resistors R56 and R57 and a feedback resistor R58. The resistors R59 and R60 set the operating point voltage of the comparator. As shown in FIG. 4, the output of the integrator is connected to the input of the comparator, and the output of the comparator is fed back to the input of the integrator. PW
An M oscillation circuit can be realized. The details of the variable frequency PWM control circuit will be described with reference to FIGS. The details of the operation of the variable frequency PWM control circuit of FIG. 5 will be described below. FIG. 6 shows a basic operation waveform of PWM. In FIG. 5, if the input voltage is e ₁ and the output of the comparator is e ₀ , the integrator output e _I has the relationship of equation (1). E _I = − (e ₁ −e ₁ ) · t (1) Now, when the comparator output e ₀ becomes e ₀ = Vcc, the integrator output e _I decreases. For this, when the from e _a e _b times the voltage falls until the t _1, t ₁ is the following is obtained from equation (1). [0044] _{t 1 = Δe / Vcc-e} 1 ... (2) However, Δe = e _a -e _b, the comparator output of the e ₁ reaches e _b becomes e ₀ = 0. As a result, the input of the integrator slide into increased becomes only e _1, when the time until e _I reaches e _a and t _2, the following equation is obtained. T ₂ = Δe / e ₁ (3) From the above, the output e ₀ of the comparator is a square wave signal that becomes Vcc during t ₁ and 0 during t ₂ . Assuming that the conduction rate of this square wave is α and the frequency is f, α and f are obtained from the following equations from equations (2) and (3). Α = t ₁ / t ₁ + t ₂ = Δe / Vcc−e ₁ / Δe / (Vcc−e ₁ ) + Δe / e ₁ = E ₁ / Vcc (4) f = 1 / t ₁ + t ₂ = 1 / Δe / (Vcc−e ₁ ) + Δe / e ₁ = (Vcc−e ₁ ) e ₁ / Δe · Vcc (5) When e ₁ is deleted by substituting equation (4) into equation (5), (6)
Get the expression. F = Vcc · α (1−α) / Δe (6) From equation (4), if Vcc is constant, the conduction ratio α is proportional to e ₁ . Further, assuming that Δe is constant from the equation (6), the frequency f is represented by a square function of α. That is, with a simple circuit configuration of an integrator and a comparator, a variable frequency PWM circuit capable of controlling the PWM duty ratio α in proportion to the control input voltage and controlling the frequency f in a square function relationship is realized. it can. FIG. 7 shows variable frequency characteristics and duty characteristics of the above-mentioned variable frequency PWM circuit, and FIG. 8 shows operation waveforms. Maximum frequency is about 10kHz, 5kHz, 2.5kHz
The case of z is shown. Frequency characteristic is PW
The maximum frequency is obtained when the duty of M is around 50%, and the frequency decreases as the duty decreases and increases, that is, the characteristic of the square function is shown. Also, the duty characteristic is good in linearity and can be controlled in a wide range from 0 to 100%. That is, the duty can be controlled with good linearity and can be controlled to a variable frequency, as will be described later, even when a device having a low swing speed of a power MOSFET for driving a motor is used, a sufficient PWM control range can be obtained. Can be expanded. Therefore, this method can be said to be an effective method particularly when driving the H-bridge chopper used in the electronic throttle control device or the like at a high frequency. Returning to FIG. 4, next, current detection of 53, 54
Is described below. In the current detection circuit 53, the input resistors R70 and R71 and the output resistor R7
2, an operational amplifier OP4 having R73 is used to amplify the battery current flowing through the H-bridge chopper, which is detected as a voltage by the shunt resistor 9. The battery current is an intermittent current synchronized with the PWM as can be seen from FIGS. Therefore, it is not preferable as a feedback signal for current control. Therefore, a sample-and-hold circuit is configured by the analog switch ASW and the capacitor C53 shown in the current detection circuit of FIG. 4, and the intermittent detection voltage is eliminated. That is, the PWM via the buffer 55 described above
A method is used in which the voltage is held in the capacitor C53 while the battery current detection value is in the OFF period in synchronization with the signal.
As a result, continuous motor current can be simulated from intermittent battery current. The logic circuit 54 is an AND gate 54
a, 54b, and an OR gate 54c. Based on the forward and reverse rotation signals of the motor from the microcomputer and the PWM signal,
The switching signal and the PWM signal are supplied to the H bridge chopper 7 to drive the motor 8. Note that C70 and C71 of the H-bridge chopper are filter capacitors. FIG. 9 shows a circuit diagram of the H-bridge chopper. In a chopper circuit using a power element, FIG.
As shown in FIG.
There is a delay in the flow of the actual current with respect to the signal, resulting in an uncontrolled range. This effect becomes more pronounced as the PWM frequency increases. Therefore, the variable frequency PWM method of the present invention described above may be used. That is, the problem can be solved by a variable frequency method in which the frequency is reduced when the duty of the PWM at which the influence of the turn-on and turn-off delays is large is small and large. FIG. 11 shows a step response waveform of the motor current in the electronic throttle using the microcomputer and the analog system of the present invention. It is characterized by responding at high speed by analog current control. As described above, according to the present invention, an inexpensive microcomputer having a low calculation speed can be used in an electronic throttle control device for a vehicle, so that the cost of the control device can be reduced. In addition, the control accuracy is improved by increasing the response of the motor current, the control range is expanded by the variable frequency, the electromagnetic noise is reduced by the motor pulsating current by increasing the frequency of the chopper, and the printed circuit board is simplified by the simple analog current control hardware. The cost of the control unit can be reduced due to a drastic reduction in wiring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control system configuration diagram of an electronic throttle control device according to an embodiment of the present invention. FIG. 2 is a software processing time chart for analog control and microcomputer control according to an embodiment of the present invention. FIG. 3 is a control block diagram of an electronic throttle control device according to one embodiment of the present invention. FIG. 4 is a detailed diagram of a hardware configuration of an electronic throttle control device according to one embodiment of the present invention. FIG. 5 is a variable frequency PWM control circuit diagram of the electronic throttle control device according to one embodiment of the present invention. FIG. 6 is a diagram illustrating the operation principle of a variable frequency PWM control circuit of the electronic throttle control device according to one embodiment of the present invention. FIG. 7 is an operation characteristic diagram of the variable frequency PWM control circuit of the electronic throttle control device according to one embodiment of the present invention. FIG. 8 is an operation explanatory diagram of a variable frequency PWM control circuit of the electronic throttle control device according to one embodiment of the present invention. FIG. 9 is a configuration diagram of an H-bridge chopper of the electronic throttle control device according to one embodiment of the present invention. FIG. 10 is a diagram illustrating the operation of an H-bridge chopper of the electronic throttle control device according to one embodiment of the present invention. FIG. 11 is a step response characteristic diagram of current control of the electronic throttle control device according to one embodiment of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Osuka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-9-42031 (JP, A) JP-A-8-303285 (JP, A) JP-A-6-54591 (JP, A) JP-A-61- 93251 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02D 45/00

Claims (1)

(57) [Claims 1] A chopper circuit for controlling the output torque of a motor by chopper-controlling a current flowing to a DC motor for driving a throttle valve for an automobile, and PWM control for the chopper circuit. An analog type current control circuit for supplying a signal, an opening detection value from a throttle valve opening detecting means for detecting an opening of the throttle valve, and an opening command of the throttle valve to calculate the opening of the throttle valve. A microcomputer-type electronic throttle valve control device for a vehicle, comprising: a throttle valve opening calculation unit that performs an operation of inputting an opening detection value from two opening detection means; and a throttle valve opening command. An input terminal for receiving a PWM current command to the analog type current control circuit; And a rotational direction signal output terminal for outputting said by digital calculation from opening detection value of the throttle valve and the opening command of the throttle valve PW
The analog current control circuit obtains an M current command value and outputs it to the output terminal. The analog current control circuit outputs an analog signal from current detection means for detecting a current intermittently flowing to a power element constituting the chopper circuit and an analog signal from the microcomputer. A PWM control signal to the chopper circuit is obtained by an analog operation based on the current command and the current detection means is connected in series with the motor sampled and held during a conduction period of a power element constituting the chopper circuit. An average current flowing through the motor is calculated based on a terminal voltage of the connected resistor.The analog current control unit calculates a deviation between a current command from the microcomputer and the calculated average current. Analog PWM control for controlling the pulse width of the chopper circuit according to the deviation output as the analog signal The analog PWM control means is a variable frequency PWM control; and the variable frequency PWM control is to control the relationship between the duty and the PWM frequency in a square function relationship. An electronic throttle valve control device for a vehicle, comprising: